Synthesis and bio-activities of bifunctional tetrahydrosalen Cu (II) chelators with potential efficacy in Alzheimer's disease therapy.

The dyshomeostasis of metal ions in the brain leads to the accumulation of excess metals in extracellular and inter-neuronal locations and the Amyloid ß peptide (Aß) binds these transition metals, which ultimately cause the Aß aggregation and severe oxidative stress in the brain. The aggregation of Aß and oxidative stress are important factors to trigger Alzheimer's disease (AD). Metal chelation therapy is a promising approach to removing metals from Aß-M species and relieve the oxidative stress. Therefore, 4 tetrahydrosalens containing benzothiazole moiety were designed and synthesized. Their biological activities for Alzheimer's disease therapy in vitro were determined by Turbidity assay, BCA protein assay, MTT assay and fluorescent probe of DCFH-DA. The results were comparing with that of non-specific chelator (cliquinol, CQ) and non-benzothiazole functionalized tetrahydrosalens, the results demonstrated that benzothiazole functionalized chelators had more efficient bio-activities in preventing Cu2+-induced Aß aggregation, attenuating cytotoxicity mediated by Aß-Cu2+ species and decrease the level of reactive oxygen species (ROS) in Cu2+-Aß treated PC12 cells than that of cliquinol and non-benzothiazole functionalized analogues.

Carbon vacancies enriched carbon nitride nanotubes for Pd coordination environment optimization: Highly efficient photocatalytic hydrodechlorination and CO2 cycloaddition.

The use of easily available solar energy to achieve pollutants efficient degradation and waste carbon resource CO2 utilization under mild conditions is highly desired. Herein, novel carbon vacancies enriched nanotubes graphitic carbon nitride (SCNT-500) has been successfully fabricated via melamine (MA) supramolecular hydrogen-bonded self-assembly in the presence of H2SO4. Pd NPs loaded carbon vacancies enriched carbon nitride nanotubes (Pd/SCNT-500) were used for photocatalytic chlorophenols hydrodechlorination and CO2 cycloaddition with styrene oxide. Up to 6.93 s-1 4-chlorophenol hydrodechlorination TOF and obviously improved CO2 cycloaddition efficiency could be realized with Pd/SCNT-500. The improved photocatalytic efficiency should be related to the morphology and carbon vacancies based Pd coordination environment optimization. Such as, the surface area increased nanotubes structure promoted light harvesting along with photoelectrons and holes generation; the carbon vacancies improved excited electrons capture, photoinduced carriers recombination inhibition along with substrates adsorption with electron rich Pd NPs. Mechanism studies not only demonstrated the important role of atomic hydrogen and Pd coordination environment optimization in the chlorophenols hydrodechlorination, but also confirmed the promotion ability of photogenerated electrons on CO2 cycloaddition.

Photocatalytic H2 Evolution from Ammonia Borane: Improvement of Charge Separation and Directional Charge Transmission.

Co/MII Fe layered double hydroxide (LDH) LDH photocatalysts have been designed from the aspect of employing stable half-filled Fe3+ to trap photogenerated electrons, adjusting the MII -O-Fe oxo-bridged structure to optimize the short-range directional charge transmission and intercalating oxometallate anions into the LDH to further improve light absorption along with electron-hole separation and non-noble metal Co NP loading and reduction to form a heterojunction. These LDH-based photocatalysts are employed for photocatalytic H2 evolution from ammonia borane in aqueous solution under visible light at 298 K. The photocatalytic H2 evolution activity is greatly improved through adjustment of the MII -O-Fe oxo-bridged structure and molybdate intercalation into the LDH. Turnover frequencies of up to 113.2 min-1 are achieved with Co/CoFe-Mo. Alongside the experimental results and materials characterization, capture experiments and in situ DRIFTS analysis are carried out to study the photocatalytic hydrogen production mechanism.

Enantioselective hydrogenation of α-ketoesters catalyzed by cinchona alkaloid stabilized Rh nanoparticles in ionic liquid.

The heterogeneous enantioselective hydrogenation of α-ketoesters catalyzed by rhodium nanoparticles (Rh NPs) in ionic liquid was studied with the stabilization and modification of cinchona alkaloids. TEM characterization showed that well-dispersed Rh NPs of about 1.96 nm were obtained in ionic liquid. The results showed that cinchona alkaloids not only had good enantiodifferentiating ability but also accelerated the catalytic reaction. Under the optimum reaction conditions, the enantiomeric excess in ethyl benzoylformate hydrogenation could reach as high as 60.9%.

Flexibility and Stability of Metal Coordination Macromolecules.

The effect of chain structure on flexibility and stability of macromolecules containing weak P-Fe metal coordination bonds is studied. Migration insertion polymerization (MIP) of FpCX Fp (1) and PR2 CY PR2 (2) (Fp: CpFe(CO)2 ; CX and CY : alkyl spacers; P: phosphine; R: phenyl or isopropyl) generates P(1/2), in which the P-Fe and Fe-P bonds with opposite bonding direction are alternatively arranged in the backbone. On the other hand, P(FpCX P) synthesized from AB-type monomers (FpCX P) has P-Fe bonds arranged in the same direction. P(1/2) is more rigid and stable than P(FpCX P), which is attributed to the chain conformation resulting from the P-Fe bonding direction. In addition, the longer spacers render P(1/2) relatively flexible; the phenyl substituents, as compared with the isopropyl groups, improves the rigidity, thermal, and solution stability of P(1/2). It is therefore possible to incorporate weak metal coordination bonds into macromolecules with improved stability and adjustable flexibility for material processing.